Heat dissipation device and centrifugal fan thereof

ABSTRACT

A centrifugal fan includes a housing and a plurality of blades received in the housing. The housing includes a base wall and a sidewall surrounding the base wall. The sidewall defines a first air outlet and a second air outlet adjacent to the first air outlet. An elongated air guiding plate is located between the first air outlet and the second air outlet. The air guiding plate includes an outer end away from the blades and an inner end adjacent to the blades. A height of the inner end of the air guiding plate in an axial direction of the centrifugal fan is smaller than a height of the outer end of the air guiding plate.

BACKGROUND

1. Technical Field

The disclosure relates to heat dissipation devices, and particularly to a heat dissipation device having an improved centrifugal fan.

2. Description of Related Art

With continuing development of the electronic technology, electronic components such as CPUs generate more and more heat that is required to be dissipated immediately. Cooling fans are commonly used in combination with heat sinks for cooling the electronic components. Since most of electronic devices that contain electronic components therein, such as a laptop computer, do not have enough space therein, a centrifugal fan which requires only a small space for installation is generally used.

Referring to FIG. 4, a heat dissipation device including a centrifugal fan 90 in accordance with related art is shown. The centrifugal fan 90 includes a housing 96 and an impeller 98 received in the housing 96. The housing 96 defines a first air outlet 91 and a second air outlet 92 perpendicular to the first air outlet 91. The first and second air outlets 91, 92 are both rectangular. A first fin unit 93 and a second fin unit 94 are arranged at the first and second air outlets 91, 92, respectively. The first fin unit 93 and the second fin unit 94 absorb heat from electronic components. In operation, the impeller 98 rotates to drive the airflow to flow towards the first and second fin units 93, 94 via the first and second air outlets 91, 92 to cool the electronic components continuously.

As indicated by arrows in FIG. 4, a difference of an amount of air of the airflow at two ends of each air outlet 91, 92 is huge, and thus a utilization efficiency of the airflow is low. In addition, a flow direction of the airflow at a rear end of each air outlet 91, 92 is substantially perpendicular to channels of the fin units 93, 94. This deflection of the airflow may cause a loss in kinetic energy of the airflow. Thus, an amount of air of the airflow flowing towards the first and second fin units 93, 94 may be greatly reduced. Heat dissipation efficiency of the heat dissipation device will thereby be further decreased.

It is thus desirable to provide a heat dissipation device which can overcome the described limitations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric, exploded view of a heat dissipation device according to a first embodiment.

FIG. 2 is a top, assembled view of the heat dissipation device of FIG. 1, with a top cover thereof omitted for purposes of illustration.

FIG. 3 is an isometric view of a bottom casing of a centrifugal fan of a heat dissipation device according to a second embodiment.

FIG. 4 is a top view of a conventional heat dissipation device with some parts thereof removed.

DETAILED DESCRIPTION

Reference will now be made to the drawing figures to describe the present heat dissipation device in detail.

FIGS. 1-2 illustrate a heat dissipation device in accordance with a first embodiment of the disclosure. The heat dissipation device includes a first fin unit 20 and a second fin unit 30 thermally connecting with electronic component(s) (not shown) for absorbing heat therefrom, and a centrifugal fan 10 for providing an airflow flowing through the first and the second fin units 20, 30 to take the heat away.

The centrifugal fan 10 includes a housing 12 and an impeller 13 including a plurality of blades 131 rotatably disposed in the housing 12. The housing 12 includes a bottom casing 11 and a top cover 14 mounted on the bottom casing 11. The top cover 14 is plate-shaped, which defines a through hole 15 at a center thereof functioning as an air inlet for the centrifugal fan 10. The bottom casing 11 includes a flat base wall 113, a sidewall 112 and an air guiding plate 19 perpendicular to the top cover 14 and the base wall 113 of the bottom casing 11. The base wall 113 defines a through hole 16 at a center thereof, corresponding to the through hole 15 of the top cover 14 and functioning as another air inlet for the centrifugal fan 10.

An outline of the base wall 113 includes an arced section 114, a first linear section 115 and a second linear section 116. The first and second linear sections 115, 116 are perpendicular to each other, and intersect with each other. The sidewall 112 extends upwardly and perpendicularly from the arced section 114 towards the top cover 14. A first air outlet 17 and a second air outlet 18 are defined corresponding to the first and second linear sections 115, 116 of the outline of the base wall 113, respectively. Each of the first and second air outlets 17, 18 is rectangular. The first air outlet 17 is perpendicular to the second air outlet 18. An air channel 117 is formed between free ends of the blades 131 and an inner surface of the sidewall 112 of the bottom casing 11. A width of the air channel 117 is gradually increased along a clockwise direction as viewed from FIG. 2 so as to increase the pressure of the airflow wherein the blades 131 rotate clockwise.

The air guiding plate 19 is positioned adjacent to a joint of the first air outlet 17 and the second air outlet 18. The air guiding plate 19 is elongated, and includes an outer end 191 connected to a junction of the first and second linear sections 115, 116 of the outline of the base wall 113 and an inner end 192 extending inwardly from the outer end 191 towards the blades 131. A minimal distance between the inner end 192 of the air guiding plate 19 and distal ends of the blades 131 is one millimeter. The air guiding plate 19 and the base wall 113 of the bottom casing 11 are integrally formed by injection molding process as a single piece. Alternatively, the air guiding plate 19 and the base wall 113 can be molded separately and then be assembled together.

The outer end 191 of the air guiding plate 19 has a horizontal top side parallel to a top surface of the base wall 113, while the inner end 192 of the air guiding plate 19 has a slanted top side extending downwardly from a distal end of the top side of the outer end 191 towards the top surface of the base wall 113. Thus, a longitudinal height of the outer end 191 of the air guiding plate 19 in an axial direction of the centrifugal fan 10 is constant, while a longitudinal height of the inner end 192 decreases gradually from the outer end 191 towards the impeller 13. A maximal longitudinal height of the air guiding plate 19 is smaller than a longitudinal height of the sidewall 112. The air guiding plate 19 has a first lateral surface 193 facing and adjacent to the first air outlet 17 and a confronting second lateral surface 194 parallel to the first lateral surface 193. The second lateral surface 194 is adjacent to and faces the second air outlet 18.

Referring to FIG. 2, the air guiding plate 19 extends inwardly from the junction of the linear sections 115, 116 of the outline of the base wall 113 towards the impeller 13. A first expanded air passage 118 increasing in width from an inside of the bottom casing 11 towards the first air outlet 17 is defined between the first lateral surface 193 of the air guiding plate 19 and the inner surface of one end of the sidewall 112 of the bottom casing 11 adjacent to the first air outlet 17. A second expanded air passage 119 increasing in width from the inside of the bottom casing 11 towards the second air outlet 18 is defined between the second lateral surface 194 of the air guiding plate 19 and the inner surface of another end of the sidewall 112 of the bottom casing 11 adjacent to the second air outlet 18.

Each of the first and second fin units 20, 30 has a rectangular configuration corresponding to the first and second air outlets 17, 18, respectively. The first and second fin units 20, 30 are located at the first and second air outlets 17, 18 and connected to a wider end of the first and second air passages 118, 119 respectively. In operation of the centrifugal fan 10, the airflow is driven to flow to the first air outlet 17 firstly, then pass across the air guiding plate 19 and finally reach the second air outlet 18, whereby the airflow leaves the first and second air outlets 17, 18 to take heat away from the first and second fin units 20, 30 at the first and second air outlets 17, 18, respectively. Without the air guiding plate 19, as indicated by the arrows in FIG. 4, the flow direction of the airflow flowing towards a right side of the first air outlet 91 is substantially parallel to air passages in a right side of the first fin unit 93, while the airflow flowing towards a left side of the first air outlet 91 forms an acute angle with air passages in a left side of the first fin unit 93. Thus, more airflow easily flows into the first fin unit 93 at the right side of the first air outlet 91, and a relatively less airflow flows into the first fin unit 93 at the left side of the first air outlet 91. Similarly, a flow direction of the airflow flowing towards a bottom side of the second air outlet 92 is substantially parallel to air passages in a bottom side of the second fin unit 94, while the airflow flowing towards an upper side of the second air outlet 12 forms an acute angle with air passages in an upper side of the second fin unit 94.

By the provision of the air guiding plate 19 between the first air outlet 17 and the second air outlet 18, as indicated by arrows in FIG. 2 of the present disclosure, a portion of the airflow which originally should flow towards the bottom side of the second air outlet 18 impinges onto the first lateral surface 193 of the air guiding plate 19 and is blocked by the guiding plate 19 to flow back into the first fin unit 20 at the left side of the first air outlet 17. Thus, an amount of air of the airflow flowing towards the bottom side of the second air outlet 18 is decreased and an amount air of the airflow flowing towards the left side of the first air outlet 17 is accordingly increased, in comparison with the conventional cooling fan of FIG. 4. Since the top side of inner end 192 of the air guiding plate 19 extends downwardly from the top side of the outer end 191 towards the base wall 113, there is still a sufficient amount of air which can flow through the air guiding plate 19 to reach the bottom side of the second outlet 18. Preferably, an angle formed between a projection of the air guiding plate 19 on the base wall 113 and the first linear section 115 of the outline of the base wall 113 is smaller than 45 degrees. Another portion of the airflow can flow through the top side of the inner end 192 of the air guiding plate 19 to reach the second air outlet 18, whereby a predetermined amount of air of the airflow flowing to the second air outlet 18 can be ensured. An air pressure at the left side of the first air outlet 17 almost equals to an air pressure at the right side of the first air outlet 17, and an air pressure at the bottom side of the second air outlet 18 almost equals to an air pressure at the upper side of the second air outlet 18, thereby increasing a heat exchange efficiency of the first and second fin units 20, 30 at the first and second air outlets 17, 18 with the airflow to increase a heat dissipation efficiency of the heat dissipation device.

Furthermore, due to the blocking of the air guiding plate 19, an amount of air of the airflow leaves the cooling fan 10 from the first air outlet 17 is more than that of the airflow leaves the cooling fan 10 from the second air outlet 18. That is, the air pressure of the airflow flowing through the first air outlet 17 is larger than the air pressure of the airflow flowing through the second air outlet 18. In use of the cooling fan, the first fin unit 20 located at the first air outlet 17 can absorb heat from a main electronic component which generates more heat, such a CPU, while the second fin unit 30 absorbs heat from a secondary electronic component which generates less heat, such as a power chip; thus, heat generated by the main electronic component and the secondary electronic component can be efficiently carried away simultaneously, thereby increasing utilization efficiency of the airflow generated by the cooling fan 10.

FIG. 3 shows a bottom casing 40 of a centrifugal fan in accordance with a second embodiment. The difference between this bottom casing 40 and the bottom casing 11 illustrated in the first embodiment lies in the air guiding plate 49. The air guiding plate 49 of this embodiment is a frustum of a triangular pyramid. The air guiding plate 49 has a thickness increasing gradually along a top-to-bottom direction thereof. That is, a size of a transverse section of the air guiding plate 49 gradually increases along a longitudinal direction from a topmost end towards a bottommost end of the air guiding plate 49. The air guiding plate 49 includes a first lateral surface 44 facing and adjacent to the first air outlet 17 and an opposite second lateral surface 46 facing and adjacent to the second air outlet 18. Both the first and second lateral surfaces 44, 46 are inclined to the base wall 113. A distance between the first and second lateral surfaces 44, 46 of the air guiding plate 49 decreases gradually from an outer end 41 of the air guiding plate 49 which is adjacent to a lateral side of the base wall 113 towards an inner end 42 which is adjacent to the impeller 13 of the centrifugal fan. The first and second lateral surfaces 44, 46 intersect with each other and thus form a side edge 45 at the inner end 42 of the air guiding plate 49. The side edge 45 is inclined to the base wall 113 and spaced from the impeller 13 with an increased distance along the bottom-to-top direction of the air guiding plate 49. A height of the guiding plate 49 gradually decreases along a direction from the outer end 41 toward the inner end 42; thus, a top face (not labeled) inclined downwardly from the outer end 41 toward the inner end 42.

When the airflow flows from the first air outlet 17 through the air guiding plate 49 and towards the bottom side of the second air outlet 18, a portion of the airflow impinges on the first lateral surface 44 of the air guiding plate 49 and is blocked back into the first fin unit 20 at the left side of the first air outlet 17. When the airflow impinges on the first and second lateral surfaces 44, 46 of the air guiding plate 49, each impinged point is a sound source that generated a narrow band noise. Because the first and second lateral surface 44, 46 of the air guiding plate 49 are inclined to the base wall 113, the time at which each noise generated is different. Therefore, the narrow band noises have different frequencies. Thus, the noises will not be superposed to generate a noise with a large amplitude. That is, the noise level generated by the airflow blowing on the air guiding plate 49 near the first and second air outlet 17, 18 is within a tolerable range.

It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A centrifugal fan comprising: a plurality of blades; a housing for receiving the blades therein, the housing comprising a base wall and a sidewall surrounding the base wall, the sidewall defining a first air outlet and a second air outlet adjacent to the first air outlet; and an elongated air guiding plate being located between the first air outlet and the second air outlet, the air guiding plate comprising an outer end away from the blades and an inner end adjacent to the blades, a height of the inner end of the air guiding plate in an axial direction of the centrifugal fan being smaller than a height of the outer end of the air guiding plate.
 2. The centrifugal fan as described in claim 1, wherein a maximal height of the air guiding plate is smaller than a height of the sidewall.
 3. The centrifugal fan as described in claim 1, wherein a distance between the inner end of the air guiding plate and distal ends of the blades is no smaller than one millimeter.
 4. The centrifugal fan as described in claim 1, wherein an outline of the base wall comprises an arced section, a first linear section and a second linear section connected between two opposite ends of the arced section, the first and second linear sections corresponding to the first and second air outlets, respectively, the air guiding plate extending inwardly from a junction of the two linear sections towards the blades.
 5. The centrifugal fan as described in claim 4, wherein an airflow generated by the blades first reaches the first linear section and then the second linear section, and an angle formed between the air guiding plate and the first linear section is smaller than 45 degrees.
 6. The centrifugal fan as described in claim 1, wherein the height of the outer end of the air guiding plate is constant, while the height of the inner end of the air guiding plate decreases gradually from the outer end towards the blades.
 7. The centrifugal fan as described in claim 6, wherein the air guiding plate comprises a first lateral surface facing and adjacent to the first air outlet and a confronting second lateral surface facing and adjacent to the second air outlet, the first lateral surface being parallel to the second lateral surface.
 8. The centrifugal fan as described in claim 1, wherein a size of a transverse section of the air guiding plate gradually increases along a longitudinal direction from a topmost end of the air guiding plate towards a bottommost end thereof.
 9. The centrifugal fan as described in claim 8, wherein the air guiding plate comprises a first lateral surface facing and adjacent to the first air outlet and a confronting second lateral surface facing and adjacent to the second air outlet, the first and second lateral surfaces intersect with each other and thus forms a side edge at the inner end of the air guiding plate.
 10. A heat dissipation device comprising: a centrifugal fan comprising a housing and a plurality of blades received in the housing, the housing comprising a base wall and a sidewall surrounding the base wall, the sidewall defining a first air outlet and a second air outlet adjacent to the first air outlet, an elongated air guiding plate being located between the first air outlet and the second air outlet, the air guiding plate comprising an outer end which is adjacent to a side edge of the base wall and an inner end which is adjacent to the blades, a height of the inner end of the air guiding plate in an axial direction of the centrifugal fan being smaller than the height of the outer end of the air guiding plate; and a first fin unit and a second fin unit received in the first air outlet and the second fin unit, respectively.
 11. The heat dissipation device as described in claim 10, wherein a minimal distance between the inner end of the air guiding plate and the blades is one millimeter.
 12. The heat dissipation device as described in claim 10, wherein the height of the air guiding plate decreases gradually from the outer end towards the inner end, a maximal height of the air guiding plate is smaller than a height of the sidewall.
 13. The heat dissipation device as described in claim 12, wherein the air guiding plate comprises a first lateral surface facing and adjacent to the first air outlet and a confronting second lateral surface facing and adjacent to the second air outlet, the first lateral surface being parallel to the second lateral surface.
 14. The heat dissipation device as described in claim 12, wherein a size of a transverse section of the air guiding plate gradually increases along a longitudinal direction from a topmost end of the air guiding plate towards a bottommost end thereof.
 15. The heat dissipation device as described in claim 10, wherein a distance between the inner end of the air guiding plate and the blades is gradually increased along the axial direction of the centrifugal fan from a bottom to a top thereof. 